Seminars in respiratory infections
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Community-acquired pneumonia (CAP) is the most common serious infection encountered in medical practice, with 1% to 10% of patients requiring admission to a hospital. The mortality rate of patients admitted is considerable, ranging from 5% to 25%. Motivated by the results of the British Thoracic Society (BTS) study, different investigators have identified several risk factors associated with a high mortality rate. ⋯ Pneumonia- and non-pneumonia-related complications are often observed. Adverse prognostic factors that have been reported in several studies are: advanced age, the presence of comorbidities, development of septic shock, need for mechanical ventilation (including use of positive end-expiratory pressure and FiO2 >60%), development of adult respiratory distress syndrome, progression of radiographic abnormalities, bacteremia (especially when due to P aeruginosa), non-pneumonia-related complications, and inadequate antibiotic treatment. To reduce mortality, prospective studies focusing on adverse prognostic factors at the start of and during antibiotic treatment are urgently needed at all three stages.
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The nature of the causative organisms involved in community-acquired pneumonia has always attracted the interest of investigators. Despite multiple studies using different methodological approaches, it remains a matter of controversy because a reliable cause cannot be obtained in a significant percentage of cases, even when using more sophisticated diagnostic procedures. ⋯ Recently, common respiratory pathogens such as the pneumococcus or Haemophilus influenzae, among others, showed a progressive tendency to develop resistance to penicillins and other antibiotics. Although this phenomenon has a variable impact among different countries, its growing importance is changing the classical therapeutic approach to community-acquired pneumonia.